components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/call_stack_manager.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_METRICS_LEAK_DETECTOR_CALL_STACK_MANAGER_H_
+#define COMPONENTS_METRICS_LEAK_DETECTOR_CALL_STACK_MANAGER_H_
+
+#include <stdint.h>
+
+#include <unordered_set>
+
+#include "base/macros.h"
+#include "components/metrics/leak_detector/custom_allocator.h"
+#include "components/metrics/leak_detector/stl_allocator.h"
+
+namespace metrics {
+namespace leak_detector {
+
+// Struct to represent a call stack.
+struct CallStack {
+  uint32_t depth;                        // Depth of current call stack.
+  const void** stack;                    // Call stack as an array of addrs.
+
+  size_t hash;                           // Hash of call stack.
+};
+
+// Maintains and owns all unique call stack objects.
+class CallStackManager {
+ public:
+  CallStackManager();
+  ~CallStackManager();
+
+  // Returns a CallStack object for a given call stack. Each unique call stack
+  // has its own CallStack object. If the given call stack has already been
+  // created by a previous call to this function, return a pointer to that same
+  // call stack object.
+  //
+  // Returns the call stacks as const pointers because no caller should take
+  // ownership of them and modify or delete them.
+  const CallStack* GetCallStack(int depth, const void* const stack[]);
+
+  size_t size() const {
+    return call_stacks_.size();
+  }
+
+ private:
+  // Allocator class for unique call stacks.
+  using CallStackPointerAllocator = STLAllocator<CallStack*, CustomAllocator>;
+
+  // Hash operator for call stack object given as a pointer.
+  // Does not actually compute the hash. Instead, returns the already computed
+  // hash value stored in a CallStack object.
+  struct CallStackPointerStoredHash {
+    size_t operator() (const CallStack* call_stack) const {
+      return call_stack->hash;
+    }
+  };
+
+  // Equality comparator for call stack objects given as pointers. Compares
+  // their stack trace contents.
+  struct CallStackPointerEqual {
+    bool operator() (const CallStack* c1, const CallStack* c2) const;
+  };
+
+  // Holds all call stack objects. Each object is allocated elsewhere and stored
+  // as a pointer because the container may rearrange itself internally.
+  std::unordered_set<CallStack*,
+                     CallStackPointerStoredHash,
+                     CallStackPointerEqual,
+                     CallStackPointerAllocator> call_stacks_;
+
+  DISALLOW_COPY_AND_ASSIGN(CallStackManager);
+};
+
+}  // namespace leak_detector
+}  // namespace metrics
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_CALL_STACK_MANAGER_H_